This application is for the third renewal of the Johns Hopkins Center for the Study of Childhood Asthma in the Urban Environment (CCAUE). Its long term goals have been and will continue to be to understand how exposures to indoor and outdoor airborne pollutants and allergens interact with a variety of contextual factors in the inne city to create high asthma morbidity. Asthma and obesity are public health crises that have risen concurrently over the past three decades, affecting millions of children in the U.S. and disproportionately affecting low-income minority children in urban areas. In this application, the investigators build directly on new findings from their most recent Center studies that obese children with asthma have increased susceptibility to air pollutants. Their aims are to understand these interactive effects and provide causal evidence to support these observational findings in a population of inner city African American children, a population that suffers disproportionate prevalence and morbidity from both asthma and obesity. Their Program, OBesity Enhances Susceptibility to Pollutant Effects in Asthma (OBESE ASTHMA), will study a variety of mechanisms, including increased inflammation and oxidative stress, glucocorticoid resistance, increased tidal volume and increased prevalence of sleep apnea by which exposures to pollutants such as particulate matter with aerodynamic diameter < 2.5 m (PM2.5) and ultrafine particles (UFP) lead to asthma morbidity. The investigators propose to maintain their highly talented and collaborative team of allergists, pulmonologists, epidemiologists, environmental health scientists, immunologists, toxicologists, and statisticians, as well as a highly supportive and engaged Community Advisory Board. They propose to expand their Center's capacity by developing new relationships with experts in obesity and sleep medicine to better define the role of obesity and potential mediating factors, such as sleep apnea, on susceptibility to air pollution in children. They capitalize on recent advances in technology to better understand components of particulate matter that contribute to morbidity. Since obesity and asthma have been identified as health crises of epidemic scale, their study findings will have a high potential to impact policy and clinical practice guidelines. The investigators expect to translate their findings into practical targeted interventions to improve pediatric asthma healt in the highest risk subpopulation. Because there are existing and emerging methods to both prevent and treat obesity and sleep apnea, there are ripe opportunities to test the impact of these treatments as novel non-pharmacological means to treat asthma in the subset that are overweight or obese. The aims of the Center, led by Center Director and co-Director, Drs. Hansel and Diette, will be answered in 3 Projects (2 human and 1 animal project) supported by Administrative, Environmental, Data, and Community Outreach Cores.